Increased Neonatal Morbidity Among Patients With Congenital Hypothyroidism

Patients with congenital hypothyroidism are more likely to have congenital malformations and neonatal morbidity.

Neonatal morbidity and congenital malformations are more common among patients with congenital hypothyroidism (CH) compared to those without, according to study findings in The Journal of Clinical Endocrinology & Metabolism

Previous research has shown that CH is often associated with an increased risk of developing chronic diseases and neurological conditions compared with the general population. Researchers conducted a nationwide, population-based cohort study to determine the incidence of congenital malformations in patients with primary CH.

Data were collected from 4 national population-based registers in Finland. All patients included in this study were aged younger than 2 years and were diagnosed with primary CH based on the International Classification of Diseases (ICD), 9th and 10th revisions. 

Patients were also included if they received a prescription for levothyroxine when they were aged younger than 1 year. Prescription data was collected from the Prescription Register of The Social Insurance Institution of Finland from 1993 through 2017. Patients with end-stage renal disease or panhypopituitarism were excluded from the study. 

A total of 531 full-term patients were identified for inclusion. There were 181 boys and 350 girls diagnosed with primary CH, with 4 patients being twins. The average age of the mothers at childbirth was 29.6 years (95% CI, 29.2-30.1 years). 

Analysis was conducted among patients without known genetic or chromosomal abnormalities (n=438; 148 boys and 290 girls).

Our data reveal a striking increase in the cumulative incidence of specific developmental disorders in CH.

There was an increased incidence of neonatal morbidity among patients born with CH compared with those without CH. Newborns with CH experienced more prolonged gestation (11.2%; >42 weeks) compared with those without prolonged gestation (2.8%; P <.001).

Compared with the group with CH, patients without CH had lower incidence of comorbidities, such as neonatal jaundice (11.2% vs 2.0%, P <.001), hypoglycemia (8.9% vs 2.8%, P <.001), metabolic acidemia (3.2% vs 1.1%; P =.007), and respiratory distress (3.9% vs 1.3%; P <.003) compared with the control group.

Congenital malformations or deformations were more common in patients diagnosed with CH (15.1%) compared with patients without CH (7.4%).

Study limitations are the exclusion of some malformation types, potential reporting bias, and lack of data regarding certain conditions. 

“Our data reveal a striking increase in the cumulative incidence of specific developmental disorders in CH [congenital hypothyroidism],” the study authors wrote. “In addition, it should be noted that milder disorders are diagnosed and treated in primary health care and are therefore not even recognized in this study.”


Danner E, Jääskeläinen J, Niuro L, et al. Comorbidity in congenital hypothyroidism – a nationwide population-based 2 cohort study. J Clin Endocrinol Metab. Published online June 6, 2023. doi:10.1210/clinem/dgad334